There’s nothing unexpected here so far. You’re causing yourself unnecessary anxiety 🙃.

With trend data or data over time, if you look at a small period of time, the only knowledge you get is limited to that period of time.

If we look at that small period of time where it behaves differently, we can say an event, independent of other events, caused the change. If we look at historical data, we can likely see that similar events caused similar changes. If we then take the data of the event itself, say the average temperature of the El Niño, and compare it to historical El Niños, we will likely see it is a worse El Niño, and maybe see that they have been worsening over time as well. That becomes evidence of climate change too.